Immunogold labeling using VirB6-specific antisera to localize Virb6-WT and its variants in A. tumefaciens.
A, results of immuno-EM analysis with VirB6-specific antisera and colloidal gold–labeled protein A of A. tumefaciens C58 cultivated without (−AS) or with virulence gene induction (+AS) and virB6 deletion (CB1006) transformed with empty vector pTrc200- or pTrc200-expressing VirB6a or its variants VirB6aL18A, VirB6aF20A, VirB6aΔ(18–23), and VirB6aΔ(30–35). Gold beads are indicated by arrows. B, graphic representation of the number of gold beads per square micrometer. Values and standard deviations were calculated from three independent experiments. The p values were obtained by t test, and no significant differences were observed between strain C58 and complemented CB1006. ns, p ≥ 0.05.